Study on Approach of Static Security Assessment Accounting for Electro-thermal Coupling

A static security assessment approach considering electro-thermal coupling of transmission lines is proposed in this paper. Combined with the dynamic thermal rating technology and energy forecasting, the approach can track both the electrical variables and transmission lines’ temperature varying trajectory under anticipated contingencies. Accordingly, it identifies the serious contingencies by transmission lines’ temperature violation rather than its power flow, in this case the time margin of temperature rising under each serious contingency can be provided to operators as warning information and some unnecessary security control can also be avoided. Finally, numerical simulations are carried out to testify the validity of the proposed approach.

Fast Calculation Method of Energy Flow for Combined Electro-Thermal System and Its Application

In recent years, Combined electro-thermal system has developed rapidly. In order to provide the initial data for the analysis of the combined electro-thermal system, a practical energy flow calculation method for the combined electro-thermal system is proposed in this paper. Based on the detailed analysis of the topology structure of the heating network and its hydraulic and thermodynamic model, the forward-backward sweep method for the heat flow of the heating network is established, which is more suitable for the actual radial heating network. The electric and thermal coupling model for heating source, such as thermoelectric unit and electric boiler is established, and the heat flow of heating network and the power flow of power grid are calculated orderly, thus a fast calculation method for the combined electro-thermal system is formed. What’s more, a combined electro-thermal system with two-stage peak-shaving electric boiler is used as the example system. This paper validates the effectiveness and rapidity of this method through the example system, and analyzes the influence for the energy flow of combined electro-thermal system caused by the operating parameters such as the installation location of electric boiler, the outlet water temperature of heat source and the outlet flow rate, etc.

典型储液类结构流-固耦合问题的扩展研究

为了明晰流体与固体耦合力学机理及其相互作用力,本文以典型储液类流固耦合问题为研究对象,综合应用变积方法、Lagrange乘子法和对合变换法,建立了非保守流固耦合问题的一类变量和二类变量的拟变分原理。经推导其驻值条件得到一类变量和二类变量流固耦合问题的控制方程。应用Lagrange乘子表示流固耦合界面处耦合因子,分别给出应用流体力学变量和固体力学变量表达的耦合因子。将拟变分原理应用于有限元素法,建立了流-固耦合动力学的协调元和杂交元计算模型。本文对流固耦合问题的变分方法发展和提高计算效率具有重要作用。

A study on temperature monitoring method for inverter IGBT based on memory recurrent neural network

The power module of the Insulated Gate Bipolar Transistor(IGBT)is the core component of the traction transmission system of high-speed trains.The module's junction temperature is a critical factor in determining device reliability.Existing temperature monitoring methods based on the electro-thermal coupling model have limitations,such as ignoring device interactions and high computational complexity.To address these issues,an analysis of the parameters influencing IGBT failure is conducted,and a temperature monitoring method based on the Macro-Micro Attention Long Short-Term Memory(MMALSTM)recursive neural network is proposed,which takes the forward voltage drop and collector current as features.Compared with the traditional electricalthermal coupling model method,it requires fewer monitoring parameters and eliminates the complex loss calculation and equivalent thermal resistance network establishment process.The simulation model of a highspeed train traction system has been established to explore the accuracy and efficiency of MMALSTM-based prediction methods for IGBT power module junction temperature.The simulation outcomes,which deviate only 3.2% from the theoretical calculation results of the electric-thermal coupling model,confirm the reliability of this approach for predicting the temperature of IGBT power modules.

Behaviour of Coupled Modes in a Simple Nonlinear Air-Sea Interaction Model

In this article, a model with the simplest framework is constructed and solved analytically. It is shown that intraseasonal wave coexists with interannual variation, and ENSO cycle arises from coupled Kelvin wave destabilisation. Its irregularity can be related to reasonable model parameters. External processes have some important effects on nonlinear air-sea interaction modes.

STATIONARY SOLUTION FOR A STOCHASTIC LINARD EQUATION WITH MARKOVIAN SWITCHING

This paper considers a stochastic Lienard equation with Markovian switching. The Feller continuity of its solution is proved by the coupling method and a truncation argument. The existence of a stationary solution for the equation is also proved under the Foster-Lyapunov drift condition.

STATIONARY DISCONTINUITY AND FLUTTER INSTABILITY OF WAVE PROPAGATION IN ELASTO-PLASTIC SATURATED POROUS MEDIA

In the present work a model based on the Biot theory for simulating coupled hydrodynamic behavior mi saturated porous media is utilized with integration of the inertial coupling effect between the solid-fluid phases of the media into the model. The non-associated Drucker-Prager criterion to describe nonlinear constitutive behavior of pressure dependent elasto-plasticity for the media is particularly considered. With no consideration of compressibility of solid grains and the pore fluid, the discontinuity and instability of the wave propagation in saturated porous media axe analyzed for the plane strain problems in detail. The critical conditions of stationary discontinuity and flutter instability in the wave propagation are given. The results and conclusions obtained by the present work will provide some bases or clues for overcoming the difficulties in numerical modeling of wave propagation in the media subjected to dynamic loading.

基于PADC-PCNN与平稳小波变换多焦距绿色植株图像融合算法

[目的/意义]构建绿色植株三维点云模型需大量清晰图像,受镜头景深限制,在采集大纵深植株图像时图像会部分失焦,导致出现边缘模糊、纹理细节丢失等问题,现有的处理算法难以兼顾处理质量和处理速度。本研究目的是提出一种新型算法,提高融合图像质量问题的同时兼顾处理速度。[方法]提出了一种基于非下采样剪切波变换(Non-Subsampled Shearlet Transform,NSST)的参数自适应双通道脉冲耦合神经网络(Parameter Adaptation Dual Channel Pulse Coupled Neural Network,PADC-PCNN)与平稳小波变换(Stationary Wavelet Transform,SWT)的植株图像融合方法。首先对植株的RGB图像进行通道分离,针对含纹理细节等特征较多的G通道进行NSST分解,低频子带使用梯度能量融合规则,高频子带使用PADC-PCNN融合规则;对轮廓信息和背景信息多的R、B通道,采用速度快且具备平移不变性的平稳小波变换,用以抑制伪Gibbs效应。自建了480幅图像共8组数据,以光照环境、距离和植株颜色为变量,同时采集不同焦距图像验证算法性能。[结果和讨论]基于PADCPCNN-SWT算法与常用的快速导向滤波算法(Fast Guided Filter,FGF)、随机游走算法(Random Walk,RW)、非下采样剪切波变换的脉冲耦合神经网络算法(Nonsubsampled Shearlet Transform based Pulse-Coupled Neural Network,NSST-PCNN)、平稳小波变换算法(Stationary Wavelet Transform,SWT)和非下采样剪切波变换的参数自适应双通道脉冲耦合神经网络(Nonsubsampled Shearlet Transform based Parameter-Adaptive Dual-Channel Pulse-Coupled Neural Network,NSST-PADC)等五种算法相比,在清晰度上比前四种算法分别提高了5.6%、8.1%、6.1%和17.6%,在空间频率上比前四种算法分别提高了2.9%、4.8%、7.1%和15.9%,而相较于融合效果最好的NSSTPADC算法在处理速度方面平均提升200.0%,同时调焦范围约6 mm。[结论]本研究提出的基于PADC-PCNNSWT多焦距图像融合算法实现了在保障融合质量的同时,提高了融合图像的效率,为搭建绿色植株三维点云模型提供高质量数据的同时节省了时间。

用机电耦合模型研究转子系统的非平稳过程

建立恰当的转子系统模型，对非平稳过程进行正确完备的描述是进行转子系统设计、实施状态监测和故障诊断的关键。通过考虑驱动电机的影响，建立了异步电机-受驱转子系统的机电耦合数学模型，并利用该模型对机电转子系统由串联补偿电容和负载波动引起的两种机电耦合非平稳过程进行了数值研究。研究结果表明：建立的机电耦合模型可以多方位地研究转子系统在非平衡过程中的机电耦合动力学规律。

基于多尺度线调频基稀疏信号分解的电力系统非平稳振荡信号特征提取

随着电力电子装置在源-网-荷侧的大规模应用,电力系统功率振荡表现出较强的非平稳特性和模式耦合性。本文提出一种基于多尺度线调频基稀疏信号分解的电力系统非平稳振荡信号特征提取方法。多尺度线调频基稀疏信号分解方法能够在动态的时间支撑区内对信号进行投影分解,逐次获得能量最大的信号分量,具有良好的时频聚集性,特别适用于非平稳振荡信号的分解。电力系统的功率振荡信号本质上是一种多模态时变振动系统响应信号。首先通过多尺度线调频基稀疏信号分解方法得到多个单模态振动响应信号,然后根据单模态振动响应特性采用最小二乘法进行振荡特征的提取。仿真算例和实例证明了该方法在电力系统非平稳振荡信号特征提取中的有效性和适应性。

基于PCNN的图像融合新方法

本文提出了一种基于PCNN的新型图像融合算法。首先,对待融合的两幅图像进行平稳小波分解得到两组多尺度图像;接着,取其中任意一组作为主PCNN的输入、另一组相应的图像作为从PCNN的输入,在每次迭代时,经并行PCNN点火后,得到一系列多尺度融合图像;然后,对它们进行平稳小波反变换得到每次迭代的融合结果;最后,计算每次迭代结果的信息熵,取信息熵值最大的融合图像作为最终结果。大量的实验以及与其它融合算法的比较分析,表明了本文算法的有效性和优越性。

Markov耦合与Markov过程的遍历性

本文运用耦合方法 ,真接通过无穷小算子判别随机过程的遍历性 ,得到了便于应用的遍历性定理 .

压电智能桁架随机动力特性研究

压电智能结构在航天、航空工程获得了广泛应用。但其在随机荷载作用下的动力特性研究目前还很薄弱,以往计算方法的复杂性是造成这一状况的重要原因。本文应用虚功原理建立机电耦合智能桁架结构动力有限元方程,并基于虚拟激励原理提出系统受平稳/非平稳随机激励动力响应的高效算法,该方法自动包含了全部参振振型之间的互相关项及全部随机激励之间的互相关项,本质上是精确解法。应用给出的算法对15杆平面及25杆空间智能桁架进行较宽频带激励下平稳/非平稳随机振动分析,计算结果表明了算法的可靠及高效性。本文的工作为进一步进行压电智能桁架机电耦合系统随机控制打下良好的基础。

新型酯型反相高效液相色谱填料的制备、表征及性能评价

将一种新型硅烷偶联剂 β-(3 ,4-环氧环己基 )乙基三甲氧基硅烷 (β-ECTS)与辛酸反应 ,然后再键合到硅胶上 ,得到了酯型键合固定相 .用元素分析、 1 3C固体核磁共振谱、红外光谱进行了表征 .以甲醇和水为二元流动相 ,用包括碱性、酸性和中性有机化合物在内的混合物评价了该固定相的疏水性、选择性和亲硅醇基效应 ,并考察了该填料适用的 p H范围及水解稳定性 .结果表明 ,该固定相具有较好的色谱性能 ,且在 p H=2 .5～ 7.5之间稳定性良好 。

提升静态小波与自适应PCNN相结合的图像融合算法

提出了一种新的基于提升静态小波变换与自适应PCNN相结合的图像融合算法。该方法定义一种图像单个像素的清晰度作为PCNN的链接强度,使得PCNN能根据像素清晰度的变化来自适应地调整链接强度的大小,接着对图像经提升静态小波分解得到的低频子带系数的改进拉普拉斯能量和及高频子带系数的单个像素的灰度值,分别作为自适应PCNN神经元的外部输入,并根据点火次数来确定图像融合系数。最后由提升静态小波变换的逆变换得到融合图像。实验表明,该方法在视觉效果和客观评价指标上都优于传统的基于小波变换、提升静态小波变换、提升静态小波-PCNN的图像融合算法。

电动桥式起重机负载升降过程的系统动力学模拟

从系统的角度考虑电动桥式起重机起升机构工作过程中的动力学模拟问题。首先,由系统的拉格朗日函数、约束条件和电机的磁共能定义修正的拉格朗日函数;随后,应用Hamilton原理和三相感应电机瞬态模型得出起升机构工作过程中电动桥式起重机系统的运动方程。为验证模型的效果,本文还进行了转子串电阻速度控制系统控制下的32t电动桥式起重机吊运额定负载下降过程的数值模拟,分析了高速浮动轴扭转刚度以及制动过程中转子电阻的配置方案对系统动力响应的影响。模拟结果表明,制动过程中起升机构高速浮动轴所受载荷远大于起动过程中所受载荷,制动开始时在电机转子电路中增加一级较大的外串电阻有利于减小下降制动阶段系统中的动载。

扩散过程平稳分布的存在唯一性与稳定性

用耦合方法研究扩散过程稳定性.利用KRW概率距离的对偶表示,获得平稳分布的存在唯一性、遍历性和依分布稳定性并且给出了收敛速度估计.

基于非平稳随机地震动模型的重力坝抗震可靠度分析

基于正交展开的非平稳随机地震动模型,并考虑混凝土材料的非线性和坝体与库水之间的流固耦合,对印度Koyna重力坝进行有限元分析,得到坝顶水平位移和坝颈拉应力,结合概率密度演化方法和等价极值事件的思想,获得丰富的概率信息。这为坝体结构的随机地震反应分析和可靠度研究提供新的途径。

基于相位调制的平稳非高斯桥面不平顺随机激励的模拟

在逆傅里叶变换法生成平稳高斯桥面不平顺随机激励的基础上,建立随机激励过程相位角与高阶中心矩之间的关系,通过不断调整相位角大小来改变桥面不平顺的非高斯特征,多次迭代生成给定功率谱密度、偏斜度和峭度的平稳非高斯桥面不平顺随机激励;同时,根据现场实测的桥面不平度数据,采用相位调制法重构桥面不平顺随机过程。数值算例和实测桥面不平顺的重构结果表明,该研究基于相位调制生成的平稳非高斯桥面不平顺能够满足给定目标功率谱密度、峭度和偏斜度的要求且模拟精度较高。桥面不平顺的幅值分布区域和幅值最大值随着峭度的增大而增大;偏斜度越大,桥面不平顺正偏或负偏的幅值分布区域就越大。工程应用结果表明,超高斯桥面不平顺激励的车桥振动响应最大,高斯桥面不平顺次之,亚高斯桥面不平顺激励的车桥振动响应相对较小;车辆振动对非高斯桥面不平顺激励的敏感程度大于桥梁振动。

热液系统流体输运－化学反应耦合动力学综述

输运－反应模式通过连续质量守恒方程进行描述，它表示为主要组分的Ｎ＋Ｍ个耦合的非线性偏微分方程。这些方程可以通过有限差分或有限元等数值方法进行求解。利用准静态近似法，涉及平流、分子扩散和水动力弥散作用的地球化学系统的演化在时间上通过一系列静止状态模拟出来。模拟实际地质系统的动力学实验对输运－反应耦合动力学的应用具有十分重要的影响。